P24BC

Code

Generic P — Powertrain

EVAP System Leak Detection Pump Pressure Sensor Circuit Intermittent

Brand: Generic

Type: P — Powertrain

Views: UK: 14 EN: 26 RU: 15

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Page language: EN

Causes

Corroded or loose connector at the pressure sensor or LDP
Damaged, chafed or pinched wiring between the sensor and PCM
Intermittent ground or poor reference voltage to the sensor
Faulty EVAP Leak Detection Pump pressure sensor
Intermittent failure in the LDP or its internal electronics
PCM input fault (rare) or intermittent connector at PCM

Symptoms

MIL (Check Engine) lamp illuminated intermittently
Intermittent EVAP system self-test failures; readiness incomplete
Intermittent difficulty with EVAP leak checks (test may start then stop)
No obvious drivability issues most of the time

What to check

Read freeze frame and monitor PIDs when code set; note conditions
Scan for additional EVAP-related codes
Visually inspect connectors and harness along route from PCM to LDP
Backprobe pressure sensor signal, 5V reference and ground while provoking the fault
Wiggle test harness and connectors while watching live data for dropouts
Use a lab scope (preferred) to look for intermittent signal, noise, or spikes

Signal parameters

Sensor typically uses a 5 V reference from PCM; verify ~5.0 V at reference pin (±0.25 V)
Pressure sensor output: an analog voltage that changes with pressure (commonly ~0.5–4.5 V depending on pressure and design)
Sensor ground: continuity to chassis/PCM ground, low resistance (
When LDP runs during test, signal should change smoothly without sudden dropouts or spikes
Open-circuit or short to battery/ground will cause signal to go to fixed rail or 0 V

Diagnostic algorithm

Verify and record freeze frame, MIL history and other stored codes.
With scan tool, reproduce the EVAP LDP test sequence and watch live data (pressure sensor voltage/PID) to capture the intermittent event.
Visually inspect connectors at the LDP and underhood/near fuel tank for corrosion, water intrusion, or loose pins. Repair or reseat as needed.
Backprobe and measure: a) 5 V reference present with ignition on, b) sensor output voltage varies when pump runs, c) solid ground present. Note any intermittent loss.
Wiggle the harness and connectors while monitoring the signal; look for intermittent faults caused by movement.
If intermittent is not captured, use an oscilloscope to monitor the sensor signal and reference for noise, dropouts or transient shorts.
Perform continuity and resistance tests on wiring between sensor and PCM; check for shorts to power or ground and for open circuits. Repair any damaged wiring.
If wiring and connectors check good, bench-test or swap the pressure sensor / LDP with a known-good unit to confirm sensor fault.
After repairs or replacement, clear codes and perform the EVAP LDP self-test or a road/evap test cycle to confirm the fault does not return.
If fault persists with good wiring and sensor, inspect PCM connector and grounds; consider PCM input fault and consult manufacturer resources.

Likely causes

Loose/corroded connector at the pressure sensor or pump (most common)
Broken wire or intermittent short to battery/ground where harness flexes
Faulty pressure sensor inside the LDP
Poor ground or 5V reference intermittently lost

Fault status

⚠️ Status

Intermittent malfunction detected in EVAP Leak Detection Pump pressure sensor circuit — signal intermittently open/short/out-of-range during EVAP self-test.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours